This application is claims the benefit of priority from German application no. 199 34 288.1 filed on Jul. 21, 1999, under 35 USC xc2xa7119, the full disclosure of which is incorporated herein by reference.
The invention relates to an apparatus for the mechanical treatment of workpieces.
GB 20 74 487 A discloses a device for opening a flange connection having two pincer arms which are formed by levers mounted rotatably with respect to one another. The ram of a driving piston acts on one pincer arm, while the other pincer arm is fastened rigidly to the driving piston. An actuating lever can be used to trigger a working stroke by means of which the first pincer arm can be moved towards the fixed pincer arm.
EP 0 299 477 A1 discloses a hydraulically actuated hand-held tool, such as tongs or shears, for cutting and/or deforming pieces made of high-strength material, having a hydraulic system with a pressure-medium working cylinder connected downstream in which a pressure piston moving the tool can be displaced, and the pressure medium being pumped into the working cylinder by means of a hand lever coupled to a control piston. In this case, the pressure piston moves outwards and thereby presses the two tong levers against each other by their shearing surfaces or the like. With the pressing of the shearing surfaces or the like against one another, the workpiece pressed against, for example a bolt or a pipe, is severed or worked.
Manually guided tools have been used for many years for carrying out operations on a mechanical workpiece. However, the design as a hand-held tool involves the risk of the hand or individual fingers of an operator getting between the working ends of opened arms and being crushed there during a subsequent working stroke.
DE 19542 068 A1 discloses pneumatically operated hand-held tools in which a mouth formed by moveable tong jaws is distinguished in that the mouth is shut in its open position by means of a moveable displacement body accommodated in it, for example a leaf spring, in order to prevent the unintentional ingress of foreign bodies. This in particular prevents a risk of injury by the operator""s fingers getting into the mouth.
It is furthermore known to close an apparatus for the mechanical treatment of workpieces to a sufficient extent that individual fingers of an operator no longer pass between the working ends and then to trigger the actual working stroke of the driving piston. In the case of the press-joining tool EMF 30/3L from Eckold a spacer is provided for this purpose, the spacer being pivoted, as the working ends are being closed, between the driving end of a moveable leg and the ram of the driving piston, so that transmission of the working stroke of the rain to the moveable leg is only possible if a force-transmission chain is completed. If the apparatus is not closed, an activated working stroke of the driving piston would not result in there being contact between the ram and leg, since the length of the working stroke is too short to reach the leg.
However, it has proven disadvantageous that an additional second handle is needed to pivot the spacer in, as a result of which both hands are at least temporarily needed in order to operate the apparatus. Operation is made more difficult as a result.
The object of the invention is therefore to provide a hand operated apparatus for the mechanical treatment of workpieces which make operation possible using just one hand.
This provides an apparatus, in particular with bring about a manual closing movement and the subsequent triggering of the power stroke using the same actuating element. An apparatus of this type can be operated exclusively using one hand and without any fitting work. Furthermore, an apparatus of this type can provide a comparatively large opening extent between the working ends resulting in an extended spectrum of use with regard to the workpiece regions to be mechanically treated.
In conjunction with the design of the spacer as a single-armed lever whose free end is coupled to a tension spring, disengagement of the spacer from the force-transmission chain is ensured. Only when a counter force which overcomes the tensile force of the tension spring is used is engagement of the spacer into the force-transmission chain made possible.
In addition, engagement of the spacer can be ensured exclusively if an operator is firmly pressing a one-handed operating lever. In the event of the operating force slackening slightly, provision may be made for the spacer itself to be pulled out of the force-transmission chain again during the working stroke, as a result of which the working stroke is broken off. This means additional safety, since after a working stroke is triggered the operation does not inevitably have to be completed.
The actuating element may be operable in the manner of a trigger on the apparatus handle in order to engage the spacer counter to the tension spring force. Also, a pressure point may be incorporated into the actuating path of the actuating element, which point indicates that the spacer has engaged into the force-transmission chain between the ram and pivotable apparatus, and serves as a warning of the forthcoming triggering of the working stroke.
Further refinements of the invention can be taken from the following description and from the dependent claims.